Coolers in general are well known in the art, but there are less known subsea coolers. Examples of subsea coolers, cooling a well flow such as a hydrocarbon flow, are disclosed in for example the applicant's own published application WO 2011008101 A1, which is hereby incorporated by reference in its whole, or in Norwegian patent NO 330761 B1. Other known subsea coolers are described in WO 2010110674 A2 and WO 2010110676 A2.
A compressor's function is in part dependent on the flow rate and the temperature of the medium that is to be compressed. It has been proved that cooling the medium increases the efficiency of the compressor. The need for a robust and fully-working compressor with minimum maintenance needs has proved especially important in subsea applications because of the difficulty in access with regards to remoteness and the harsh subsea environment. However, cooling a hydrocarbon flow may create, among other problems, hydrate formation. Hydrate formation occurs because water usually forms part of the hydrocarbon flow, which water is enabled to be separated out as free water when cooling the flow. Hydrates may crystallize or compact, creating danger of blockages in tubing, flow lines or pipe lines. It is therefore important that the cooling unit is adapted to the specific use, as well as the amount and composition of the medium to be cooled.
It has proved difficult to arrange a cooler system that is flexible with regards to flow rate and temperature of the well flow.
An object of the invention is therefore to provide a cooling system that is flexible with regards to the cooling needs of a lifetime cycle of a well flow.
Another object is to make sure that the cooled flow stays within a predetermined temperature range.